Explicit Dynamic Analysis for Crash Simulation

Understanding Explicit Dynamic Analysis in Modern Engineering

When a vehicle collides with a barrier, a ship hull impacts floating ice, or a structure experiences a sudden blast load, the physics involved occur within milliseconds. Traditional static analysis methods cannot adequately capture these rapid, highly nonlinear events. This is where explicit dynamic analysis becomes indispensable—a sophisticated computational approach that has revolutionised how engineers simulate and predict crash behaviour across numerous industries.

Explicit dynamic analysis solves the equations of motion using a direct integration scheme, calculating the response of a structure at each small time increment without requiring the solution of simultaneous equations. This methodology proves particularly valuable for Atlantic Canadian industries, including automotive suppliers, aerospace manufacturers, marine vessel designers, and offshore energy companies operating throughout Nova Scotia and the Maritime provinces.

At its core, explicit analysis excels when dealing with short-duration events characterised by high strain rates, large deformations, complex contact interactions, and material failure. Unlike implicit methods that iterate to find equilibrium at each time step, explicit solvers march forward in time using information from the previous state, making them computationally efficient for problems involving millions of degrees of freedom and highly nonlinear behaviour.

The Physics Behind Crash Simulation Technology

Crash simulation relies on fundamental principles of continuum mechanics, combined with advanced numerical methods to discretise both space and time. The explicit finite element method divides structures into thousands or millions of small elements, each governed by constitutive equations that describe material behaviour under extreme loading conditions.

Time Integration and Stability Considerations

The central difference method, commonly employed in explicit codes, advances the solution using a conditionally stable algorithm. The critical time step is determined by the Courant-Friedrichs-Lewy (CFL) condition, which relates to the smallest element dimension and the material's wave speed. For typical steel structures, this translates to time steps on the order of 10^-6 to 10^-7 seconds.

Engineers must carefully balance mesh refinement against computational cost. A finer mesh provides greater accuracy but reduces the stable time step proportionally. Modern crash simulations for full-vehicle models typically contain 3 to 10 million elements and require 8 to 24 hours of computation time on high-performance computing clusters, even with time steps measured in microseconds.

Material Modelling at High Strain Rates

Materials behave differently under rapid loading than under quasi-static conditions. Steel, aluminium, and polymer materials all exhibit strain rate sensitivity, where yield strength and flow stress increase with loading velocity. The Johnson-Cook and Cowper-Symonds models are frequently employed to capture this rate-dependent behaviour, with parameters calibrated through specialised high-speed testing.

For automotive-grade steels commonly processed at Maritime manufacturing facilities, strain rate sensitivity can increase yield strength by 20 to 40 percent at strain rates of 100 per second, significantly affecting energy absorption predictions. Accurate material characterisation is therefore essential for reliable crash simulation outcomes.

Industrial Applications Across Atlantic Canada

The diverse industrial landscape of Nova Scotia and the broader Atlantic region presents numerous applications for explicit dynamic analysis. From traditional manufacturing to emerging sectors, crash simulation technology supports safer, more efficient product development.

Automotive and Transportation

Automotive suppliers throughout the Maritimes produce components that must meet stringent crashworthiness requirements. Front and rear bumper systems, door intrusion beams, and structural reinforcements all require validation against federal motor vehicle safety standards. Explicit analysis enables engineers to:

• Simulate frontal, side, and rear impact scenarios according to Transport Canada and NHTSA protocols

• Optimise energy-absorbing structures for maximum occupant protection

• Evaluate component performance across multiple impact velocities, typically ranging from 8 to 56 kilometres per hour

• Assess pedestrian protection requirements for hood and fender assemblies

• Reduce physical prototype testing by 60 to 80 percent through virtual validation

Marine and Offshore Applications

Nova Scotia's extensive coastline and maritime heritage create unique demands for crash and impact analysis. Ship collision studies, ice-structure interaction, and dropped object analyses for offshore platforms all benefit from explicit dynamic methods. Engineers working on marine projects must consider:

• Vessel-to-vessel collision scenarios for port and harbour safety assessments

• Ice impact loading on hull structures operating in northern waters

• Dropped container and equipment impact on deck structures

• Mooring line snap-back and associated structural damage

• Blast and explosion effects for offshore platform safety studies

Aerospace and Defence

The aerospace sector demands exceptional precision in crash simulation, particularly for bird strike analysis, emergency landing scenarios, and ballistic protection systems. Explicit solvers handle the extreme velocities and material failure modes characteristic of these applications. Typical bird strike analyses involve impact velocities of 150 to 250 metres per second, requiring careful treatment of fluid-structure interaction and material erosion.

Software Platforms and Computational Requirements

Several commercial and open-source platforms dominate the explicit dynamic analysis landscape, each offering distinct capabilities suited to different application domains. Selecting the appropriate software depends on industry requirements, existing workflows, and specific technical needs.

Leading Commercial Solutions

LS-DYNA remains the industry standard for crash simulation, particularly in automotive applications. Its extensive material library includes over 300 constitutive models, and its contact algorithms handle complex multi-body interactions efficiently. The software supports both shared-memory parallel (SMP) and massively parallel (MPP) execution, scaling effectively to thousands of processor cores.

ABAQUS/Explicit offers tight integration with implicit analysis capabilities, facilitating sequential explicit-implicit analyses common in forming simulation followed by crash performance evaluation. Its user subroutine framework provides flexibility for implementing custom material models and loading conditions.

RADIOSS and PAM-CRASH provide additional options with particular strengths in specific industries. RADIOSS excels in aerospace bird strike and ditching analyses, while PAM-CRASH maintains a strong presence in European automotive applications.

Hardware and Infrastructure Considerations

Effective crash simulation requires substantial computational resources. A typical workstation configuration for production crash analysis includes 32 to 64 processor cores, 256 to 512 gigabytes of RAM, and fast solid-state storage for managing large result files that can exceed 100 gigabytes per simulation. Many organisations supplement local resources with cloud computing platforms, enabling on-demand access to thousands of cores for design optimisation studies.

Best Practices for Accurate Crash Simulation

Achieving reliable crash simulation results requires adherence to established methodologies and careful attention to modelling details. Engineers must balance accuracy against computational efficiency while maintaining confidence in their predictions.

Mesh Quality and Element Selection

Element quality directly influences simulation accuracy and stability. For crash applications, engineers should maintain aspect ratios below 3:1, avoid highly skewed elements, and ensure adequate mesh density in regions of expected deformation. Shell elements with five to seven through-thickness integration points typically provide sufficient accuracy for sheet metal structures, while solid elements may be necessary for thick castings and machined components.

Mesh convergence studies should verify that results remain stable as element size decreases. For automotive crash simulation, element sizes of 3 to 5 millimetres in critical regions represent current industry practice, with coarser meshes acceptable in non-deforming areas.

Contact and Connection Modelling

Accurate representation of component connections significantly affects crash behaviour prediction. Spot welds, adhesive bonds, bolted joints, and clinched connections each require appropriate modelling techniques:

• Spot welds are typically represented using beam or solid elements with failure criteria based on normal and shear forces

• Adhesive bonds employ cohesive elements or tied contacts with damage evolution models

• Bolted connections may require detailed solid element models or simplified spring representations depending on their role in energy absorption

• Self-contact algorithms must be activated for components expected to fold and buckle during impact

Validation and Correlation

Physical testing remains essential for validating simulation methodologies. Component-level tests, such as axial crush tests on rail sections or three-point bend tests on beam structures, provide data for model calibration. System-level tests then confirm that the assembled model accurately predicts overall crash behaviour.

Quantitative correlation metrics, including CORA (Correlation and Analysis) ratings, provide objective assessment of simulation-to-test agreement. Industry targets typically require CORA ratings above 0.65 for certification-level analyses, with values above 0.80 indicating excellent correlation.

Emerging Trends and Future Developments

The field of explicit dynamic analysis continues to evolve, driven by increasing computational power, advancing material technologies, and growing demands for simulation fidelity. Several trends are shaping the future of crash simulation.

Machine Learning Integration

Artificial intelligence and machine learning techniques are increasingly supplementing traditional physics-based simulation. Surrogate models trained on simulation databases can predict crash performance in seconds rather than hours, enabling rapid design exploration. Neural network approaches also show promise for accelerating material model calibration and identifying optimal mesh configurations.

Multi-Physics Coupling

Modern crash scenarios often involve multiple physical phenomena occurring simultaneously. Battery thermal runaway during electric vehicle crashes, fuel tank rupture and subsequent fire, and airbag deployment gas dynamics all require coupled multi-physics approaches. Explicit solvers are increasingly integrating with computational fluid dynamics, thermal analysis, and electromagnetics codes to address these complex scenarios.

Advanced Materials and Manufacturing

The proliferation of advanced high-strength steels, aluminium alloys, carbon fibre composites, and additive manufactured components creates new challenges for crash simulation. These materials exhibit complex failure modes, anisotropic behaviour, and manufacturing-induced variability that require sophisticated modelling approaches. Micromechanical models and multi-scale simulation techniques are emerging to address these challenges.

Partner with Maritime Engineering Expertise

Explicit dynamic analysis for crash simulation demands specialised expertise, sophisticated software tools, and substantial computational resources. Whether you are developing automotive components, designing marine vessels, or assessing structural resilience against impact loads, accurate crash simulation reduces development costs, accelerates time-to-market, and ultimately saves lives through improved safety performance.

Sangster Engineering Ltd. provides comprehensive explicit dynamic analysis services to clients throughout Nova Scotia, Atlantic Canada, and beyond. Our team combines deep theoretical knowledge with practical industry experience, delivering crash simulation solutions tailored to your specific requirements. From initial feasibility studies through detailed design validation, we support your engineering challenges with rigorous analysis and clear communication.

Contact Sangster Engineering Ltd. today to discuss how explicit dynamic analysis can enhance your product development process. Our Amherst-based team is ready to help you navigate the complexities of crash simulation and achieve your safety and performance objectives.

Partner with Sangster Engineering

At Sangster Engineering Ltd. in Amherst, Nova Scotia, we bring decades of engineering experience to every project. Serving clients across Atlantic Canada and beyond.

Contact us today to discuss your engineering needs.